Brazilians hope to avoid resistance problems

Jun 27, 2008

What if U.S. farmers could turn back the clock five years and add a residual herbicide to their Roundup Ready corn, cotton and soybean weed control programs?

No one knows for sure, but it might be possible that farmers and weed scientists wouldn't be scratching their heads trying to figure out how to deal with glyphosate-resistant horseweed, giant ragweed and pigweed.

That's the message Valent USA and other chemical company representatives were giving a group of their counterparts from two firms located in Brazil during a recent tour of farms in Illinois, Missouri, Arkansas and Tennessee.

Because of government policies, Brazilian farmers are just now beginning to adopt Roundup Ready and Roundup Ready/Bollgard stacked gene crops. The fact Brazilian growers have used little glyphosate herbicide to this point gives them a unique opportunity.

“You guys are about where we were five or six years ago,” says Jamie Nielson, herbicide product manager for Valent USA Corp who led the tour of a series of farms and research plots through central Illinois and into the Delta. “You have a chance to avoid some of the resistance issues we've seen by using residual herbicides in your cropping systems.”

The Brazilians included two employees of Sumitomo Chemical do Brasil, which is owned by Valent's parent company, and Iharabras S.A. Industrias Quimicas, a chemical distributor that operates throughout Brazil.

Although relations between their two governments have been rocky in recent years, U.S. farmers and researchers were willing to show the Brazilians how they were using Valor and other residual herbicides to control problem weeds and reduce costs.

Most agreed that applying Valor pre-emergence in cotton, corn or soybeans often can save them one application of glyphosate or even more expensive herbicides during the growing season.

“I had seen what Valor could do at lay-by in cotton, so we've been tank mixing it with the burndown in soybeans,” said Bill Ballard, an agronomist with Helena Chemical in Jonesboro, Ark. “The Valor went out 10 to 12 days before planting here, and we've had very few escapes.”

Other agronomists said more farmers have been transitioning Valor from a lay-by treatment to burndown or pre-emergence applications to prevent weeds such as Palmer amaranth (a pigweed species) from emerging. With researchers documenting more and more cases of glyphosate-resistant pigweed, Valor can help avoid more expensive herbicides.

Grower Danny Qualls of Lake City, Ark., used Valor for burndown in cotton this spring, followed by Direx at planting. He planned to come back with Roundup and Envoke to clean up any “trash” weeds that emerged after the pre-emergence treatments.

Qualls' biggest problem was a spray rig that didn't begin applying the Valor until about halfway through the first pass in the field.

No one is faulting U.S. farmers for becoming dependent on a weed control system that combined lower costs and convenience with near 100 percent weed control as the Roundup Ready crops did when they first came on the scene. But the development of herbicide tolerance or resistance in problem weeds — and the rising cost of glyphosate — is leading producers to take another look at residual compounds.

“In 2004, we had a lot of seed from resistant horseweed blown into this area,” said Tony Holder, manager of the Helena Chemical Co., located in Newport, Ark. “A number of our customers had switched to no-till, and when they applied glyphosate, it only killed about 30 percent of the weeds.

“Now we firmly believe in using a residual herbicide. Applying $8 an acre of Valor before planting can easily save you $8 worth of diesel or more later.”

Economics are also driving changes. “Five years ago you could make two applications of Roundup for $20 an acre,” said Dorsey Jones, agronomist with Helena at the Newport location. “Today that can be $50 to $60 an acre.

Monsanto has recognized the growing problem with resistance and has begun offering a program with Valent aimed at encouraging the use of a residual herbicide. “You can spray one time with Roundup and Valor,” said Jones. “If you have to spray again, Monsanto will pick up the cost.”

Growers are also showing more interest in fall applications of Valor. Last November, Malcolm Haigwood, a corn, grain sorghum and soybean producer from Newport, applied 2 ounces of Valor, 8 ounces of dicamba and 1 quart of Roundup on a field he intended to plant in corn this spring.

Because of flooding from the nearby White River, the field went underwater in March and April. Although he was forced to plant late because of the floodwater, Haigwood was able to drop a planter into the field without having to burn it down or till it.

“The only place we couldn't spray last fall was under the center pivot,” said Haigwood, referring to a strip of land where horseweed, pigweed and teaweed were growing. “If it wasn't for the herbicide mixture we put out last fall, the whole field might look like that now.”